This application is based on prior Japanese Patent Applications Nos. 2001-22855 (filed in Japan on Jan. 31, 2001), and 2001-282926 (filed in Japan on Sep. 18, 2001). The entire contents of these Japanese Patent Applications Nos. 2001-22855 and 2001-282926 are hereby incorporated by reference.
The present invention relates to an internal combustion engine, and more specifically a valve drive mechanism including intake and exhaust valve drive shafts each provided with sprocket or pulley driven by an engine crank shaft through timing chain or timing belt.
A published Japanese Patent Application Publication (Kokai) No. 2000-64814 shows a direct drive type overhead cam, valve drive mechanism having camshafts (or valve drive shafts) extending in parallel to each other above a cylinder head.
It is an object of the present invention to provide a valve drive apparatus for an internal combustion engine capable of setting a valve included angle formed between intake and exhaust valve axes to a desired value without changing an inter-shaft distance between intake valve drive shaft and exhaust valve drive shaft.
According to the present invention, a valve drive apparatus for an internal combustion engine, comprises: a first valve drive shaft adapted to be driven by the engine; a rocker cam to push a first valve of the engine by swinging about a first shaft axis of the first valve drive shaft; and a link mechanism connecting mechanically the rocker cam and the first valve drive shaft to transmit motion from the first valve drive shaft to the rocker cam. The first shaft axis of the first valve drive shaft about which the rocker cam swings is offset from a valve axis of the first valve.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.